|Dracula (1973) [Dracula's Wife]: Stabbed in the chest (off-screen) with a wooden stake (along with Barbara Lindley and Virginia Wetherell) by Nigel Davenport as she's lying in her coffin. (Only Virginia's staking is shown on-camera; the other two are off-screen.) (Thanks to PortsGuy)
The Final Programme (The Last Days of Man on Earth) (1973) [Catherine Cornelius]: Accidentally shot in the chest with a needle-gun by her brother (Jon Finch) while he's trying to kill their other brother (Derrick O'Connor) and hits her instead.
Superman II (1980) [Ursa]: Knocked into a deep pit by Margot Kidder, after Christopher Reeve manages to strip Sarah, Terence Stamp, and Jack O'Halloran of their superhuman powers. (Thanks to Rick, Robert and Michael)
Conan the Destroyer (1984) [Queen Taramis]: Impaled on the horn of a demon that she had summoned with a magic ritual.
V: The Final Battle (1984) [Pamela]: Shot in the shoulder and stomach with a ray-gun by Jane Badler on board the Visitors' space station. (Thanks to Matthew)
Solarbabies (Solar Warriors) (1986) [Shandray]: Electrocuted when she backs into a computer terminal, after the mysterious orb burns her hands. (Thanks to Rick)
The Return of Swamp Thing (1989) [Dr. Lana Zurrell]: Shot to death by Louis Jourdan. (Thanks to Rick and PortsGuy)
Puppet Master III: Toulon's Revenge (1991) [Elsa Toulon]: Shot to death by a Nazi soldier; her soul is later transferred into the Leech Woman puppet. (Thanks to PortsGuy)
Return of the Living Dead III (1993) [Lt. Col. Sinclair]: Killed by the zombies. (Thanks to Robert)
Babylon 5: Deathwalker (1994) [Jha'Dur a.k.a. Deathwalker]: Killed in an explosion when the Vorlons blow up her spaceship.
Attack of the Gryphon (Gryphon) (2007) [Queen Cassandra of Delphi]: Sacrifices herself by turning herself into mystical energy to destroy Amy Gillespie and Simone Levin during a battle of magic. (Thanks to Stephen)
Witchville (2010) [The Red Queen]: Stabbed to death by her son (Luke Goss). (Thanks to Robert)